1. Field of the Invention
The present invention relates to distance-settable photoelectric sensors that can detect the presence or absence of detection objects located closer than set distances.
2. Description of the Related Art
A known distance-settable photoelectric sensor (background-suppression (BGS) photoelectric sensor) in the related art detects the presence or absence of a detection object located closer than a set distance (for example, see Japanese Unexamined Patent Application Publication No. 2010-256182). In this distance-settable photoelectric sensor, a light receiver is provided with a two-segment photodiode. By using the principle of triangulation, a detection object located closer than a set distance is detected by utilizing the fact that the light reception position at the two-segment photodiode varies depending on the distance to the detection object. For example, if there is a detection object located at the set distance, an equal amount of light is received at a near-side (N-side) light-receiving face and a far-side (F-side) light-receiving face of the two-segment photodiode due to reflection light from the detection object. If the detection object is closer to the distance-settable photoelectric sensor than the set distance, the N-side light-receiving face receives a larger amount of light due to reflection light from the detection object. In contrast, if the detection object is farther from the distance-settable photoelectric sensor than the set distance, the F-side light-receiving face receives a larger amount of light due to reflection light from the detection object. The distance-settable photoelectric sensor detects the difference between the amount of light received at the N-side and the amount of light received at the F-side and compares the difference with a threshold value so as to detect the detection object located closer than the set distance.